Axial piston pumps are known to be used in hydraulically-actuated fuel injection systems. One exemplary axial piston pump is a hydraulic electronic unit injector (HEUI) pump assembly. The efficient operation of such pumps is significant to the overall operation of the engine. Moreover, the ability of such pumps to operate free of maintenance is important to reduce downtime of the system. While efficient operation is an important design criteria, issues such as weight, size, cost, and ease of assembly influence the overall design of such pump.
U.S. Pat. No. 6,035,828 to Anderson et al., which is incorporated herein by reference in its entirety, describes a fixed displacement, variable delivery axial piston pump for a hydraulically-actuated fuel injection system. In the system, a high pressure common rail supplies hydraulic fluid to a plurality of hydraulically-actuated fuel injectors mounted in a diesel engine. The hydraulic fluid received in the common rail is pressurized by the fixed displacement axial piston pump that is driven directly by the engine. The pump includes a plurality of pistons disposed in parallel about the central longitudinal axis of the pump. An angled camming surface or swash plate is fixed to the drive shaft and is biased against a proximal end of the pistons. Low pressure actuation fluid (e.g., lubricating oil) flows through windows in the radial outer surface of a swash plate and travels radially inward to the pistons in order to be pressurized. Reciprocation of the pistons is achieved by the rotation of the swash plate. Displacement of the pump is varied by a control valve that selectively varies the amount of pressurized fluid supplied to the pump outlet during the discharge stroke of each piston. FIG. 2 of Anderson et al. illustrates two opposed tapered roller bearing arrangements for receiving axial forces created during pump operation.
In another example, U.S. Pat. No. 6,896,491 to Trubnikov et al., which is incorporated herein by reference in its entirety, describes a fixed displacement, variable delivery axial piston pump for a hydraulically-actuated fuel injection system. Here, the fixed angle swash plate can include a cylindrical elongated portion. The elongated portion can be press-fitted over the center pump drive shaft for a secure fit. The end of the elongated portion can be a tapered end. The tapered end can frictionally engage a conical recess of gear drive mechanism such that the rotation of the center pump drive shaft is directly proportionally to the drive shaft of the engine.
While the aforementioned axial piston pump assemblies operate adequately, there is a need for an improved shaft arrangement to sufficiently withstand the rotational gear loads and the axial thrust loads. The present application is directed at overcoming one or more of the problems associated with axial piston pump assemblies of the prior art.